Anti-wheel lock systems in general provide wheel speed sensing devices, a brake pressure modulating valve and a data processing device or computer which provides an output controlling the actuation of the modulating valve in response to sensed changes in wheel speed to inhibit wheel lock with its resultant loss of lateral stability of the vehicle and increased stopping distance. Heretofore these systems have been available as a group of components which the vehicle manufacturer has had to install on each vehicle. These components were, at a minimum, the computer and the control valve and normally also included the wheel speed sensors. Once installed, the computer is then connected electrically to the sensors and to the valve and the vehicle power supply and the control valve is fluid connected to the brake chambers to the fluid reservoir and the operator modulated brake pressure source.